[Olsr-users] Received message to big to be forwarded

[Henning Rogge]

Hi,

I think olsrd (1) already can split packets along the messages... the
problem happens when a message is too large even for a UDP packet of
its own.

Henning

On Fri, Apr 17, 2015 at 2:34 PM, Ferry Huberts <(spam-protected)> wrote:
> OTOH
>
> We should be able to split packets with multiple messages into multiple
> packets as long as the messages themselves aren't to big.
> And also the reverse: merge packets for larger MTUs.
>
> IMHO olsrd should/can adapt to different MTU sizes.
>
> This most probably not go into v1 unless someone has a nice patch set (well
> tested!). But I think it's a good idea for v2.
>
>
> On 17/04/15 14:30, Henning Rogge wrote:
>>
>> The only other option I see is to set the MTU size for olsrd messages
>> to 1280-40-8=1232 bytes... which should be guaranteed for all IPv6
>> capable networks.
>>
>> Henning
>>
>> On Fri, Apr 17, 2015 at 2:25 PM, Ferry Huberts <(spam-protected)> wrote:
>>>
>>>
>>>
>>> On 17/04/15 14:22, Henning Rogge wrote:
>>>>
>>>>
>>>> On Fri, Apr 17, 2015 at 2:07 PM, Jernej Kos <(spam-protected)> wrote:
>>>>>
>>>>>
>>>>> Hello!
>>>>>
>>>>> We are seeing a lot of the following messages in our logs:
>>>>>
>>>>> Received message to big to be forwarded on digger1226(1296 bytes)!
>>>>> Received message to big to be forwarded on digger1346(1328 bytes)!
>>>>>
>>>>> The message sizes indicate that the OLSR messages that are to be
>>>>> forwarded are probably larger than the MTU (the OLSR daemon has
>>>>> multiple
>>>>> interfaces with different MTU sizes). Does this warning indicate some
>>>>> problems with propagating routing information as messages are dropped
>>>>> instead of being forwarded?
>>>>
>>>>
>>>>
>>>> The problem is that olsrd cannot fragment messages (which are flooded
>>>> through the whole mesh) hop-by-hop... which means a network with
>>>> different MTU-sizes AND large neighborhoods (which produce huge
>>>> messages) is a problem.
>>>>
>>>
>>> Yes, you should really setup a lower MTU on all your nodes
>>>
>>>> Henning Rogge
>>>>
>>>
>>> --
>>> Ferry Huberts
>
>
> --
> Ferry Huberts